Method of preparation of thermosetting resins -urea - formaldehyde melamine and doped the use of these resins as resins of impregnation

摘要

Method of manufacture of a resin urea - doped with melamine formaldehyde, characterized by the fact that it is added to a mixture of the melamine formaldehyde urea - of the ratio f / nh2 than 1,5, in aqueous medium, at a ph between 6 and 8 and at a temperature between 20 and 90 deg.c, the quantity of melamine being such that its content in the final resin is between 1 and 5% by weight, and then the reaction medium is maintained at a temperature of 80 to 103 deg.c, at a ph of 6,5 to 7,8 for 5 to 15 minutes and then at a ph of 4,5 to 5,5 until one obtains a resin having a degree of condensation.